How to fix & update outdated cc's? (Windows 10)

You didn't mention what CC you're having trouble with and you need to provide more details if you want a definite answer.

If it's one file you're having trouble with and you can't figure out which one it is do the 50/50 method. Take half of your custom content and put it in a folder somewhere then test the other half in the game. If there are no problems set those files aside and test the first half. Keep doing this until you have a batch that has a broken file. In that case, keep dividing and testing until you can narrow it down to just a few files.

This was the method recommended for TS3 items and it works well with content that's meshes and textures. Anything that uses scripts or XML tuning may need to be updated by the original creator if you can't do it yourself.